KR20070095725A - Apparatus for removing non-linear distortion in optic transmitter and removing method thereof - Google Patents

Abstract

An apparatus and a method for removing non-linear distortion in an optical transmitter are provided to minimize non-linear characteristics of electric elements by employing the smallest number of electric elements. A main signal is inputted and split(S101), wherein the main signal is inputted to at least one of a semiconductor optical amplifier, a laser diode, and a phase shifter. The amplitude and phase of the split main signals are adjusted(S102). An XGM(Cross Gain Modulation) phenomenon is induced in a semiconductor optical amplifier(S103). An output signal of the semiconductor optical amplifier is transmitted(S104).

Description

Apparatus For Removing Non-linear Distortion In Optic Transmitter And Removing Method Thereof}

1 is a schematic schematic diagram of a wireless optical communication system.

Fig. 2 is a block diagram showing each structure of a nonlinear distortion elimination apparatus for an optical transmitter according to a first embodiment of the present invention.

3 is a block diagram of a non-linear distortion elimination apparatus for optical transmission according to a first embodiment of the present invention.

4 is an exemplary diagram illustrating an RF frequency spectrum when a signal is transmitted through a wireless optical link using only DFB LD.

5 is an exemplary diagram illustrating the RF frequency spectrum of a signal injected into the RSOA through the DFB LD.

6 is an exemplary diagram illustrating an RF frequency spectrum of an ROSA output signal.

7 is an exemplary diagram showing a signal in the RSOA and an output signal according thereto.

8 is an exemplary diagram illustrating a principle of reducing IMD3 due to phase change in RSOA.

9 is a block diagram showing each structure of a non-linear distortion elimination apparatus for optical transmission according to a second embodiment of the present invention.

10 is a block diagram of a non-linear distortion elimination apparatus for optical transmission according to a second embodiment of the present invention.

11 is a flowchart illustrating a method for removing nonlinear distortion for optical transmission according to a first embodiment of the present invention.

           <Description of the symbols for the main parts of the drawings>

10: central station 20: base station

30: terminal 50: optical link

100: phase shifter 200: DFB LD 300: RSOA 400: coupler 500: photodetector 700: signal splitter

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a nonlinear distortion elimination device and a method of eliminating an optical transmitter, and more particularly, to a nonlinear distortion elimination device and a method for eliminating an optical distortion caused by a laser diode.

Modern wireless access network systems transmit not only voice signals but also data of various services. Recently, Radio-over-fiber (RoF) technology has been in the spotlight to accommodate various large-capacity services. RoF system is a system for optically modulating a plurality of RF signals to be transmitted to the wireless system at the same time. As shown in FIG. 1, the RoF system loads a plurality of data to be sent using a mixer (Mixer) (not shown) in a plurality of RF signals, and then applies them to a laser diode (LD) to supply an electrical signal. Modulates an optical signal. The signal is transmitted through the optical cable 50 and applied to a base station (20) optical receiver (PD) of a wireless system to convert an optical signal into an electrical signal to be transmitted as a wireless signal.

In order to control all the cells in a wireless system, a large number of base stations 20 are required. In such subcarrier-multiplexing (SCM) optical transmission, it is more efficient in terms of economic or system operation to control at the central station (10) than to perform all the RF control at the base station 20.

In general, optical communication transmits information using an optical field electromagnetic wave such as a laser beam, unlike an electromagnetic wave that electrically transmits a signal, a message, or another type of information. When the audio and video information is converted into an electrical signal and transmitted to the transmitter, the transmitter converts the signal into a light through a light emitting diode or a laser diode and transmits the light to a light receiving device such as an optical fiber or a photodiode. The light transmitted to the optical fiber moves at the speed of light while blinking hundreds of millions to billions of times per second, and the optical signal is kept constant by installing a repeater every 130 ~ 140km to amplify the optical signal to prevent the light intensity from being weakened. Keep it. The optical signal thus transmitted is converted back into an electrical signal in the form of light through the receiver and restored to the original audio or video information. Such optical communication has the advantage of delivering high-speed and large amounts of clear voice and video, and communication using copper lines or radio waves is significantly lower than optical communication in terms of speed and quality.

A general optical transmission system uses a light emitting device such as a light emitting diode (LED) or a laser diode to convert an electrical signal into an optical signal. That is, the electric signal is applied to the light emitting device, and modulated into an optical signal and transmitted to the light receiving device, which receives the photoelectric conversion. However, when converting an electric signal into an optical signal, a high-order intermodulation distortion (IMD) signal and a harmonic distortion signal are generated due to the laser diode and the light emitting diode having the largest non-linear characteristics. And a distortion signal and a main signal are generated together in the signal processing process of the light receiving element. In particular, since the 3rd order IMD component is close to the fundamental frequency, it is difficult to remove it with a filter at the receiving end, and it is a big problem in terms of efficient use of the frequency dimension. In all current analog direct modulation schemes, the IM (Intermodulation) of the entire system is determined by the characteristics of the light emitting device due to such nonlinear distortion. Wireless optical repeaters that are currently commercially available are also subject to this limitation. Due to the increase in mobile subscribers and mobile service providers, the bands and total input power to be serviced have increased. This demand cannot be satisfied.

In order to solve this problem, the conventional nonlinear distortion signal processing apparatus removes the distortion signal by generating a signal having the same magnitude and opposite phase as the distortion signal included in the main signal and coupling the distortion signal to cancel each other. The method, feed forward method, or a mixture thereof is used. These techniques have been proposed since 1920 and are a classic way to control the nonlinearity of RF amplifiers or mixers.

On the other hand, it is difficult to apply a feedforward method that forms a closed loop to an optical communication device that converts an electric signal into an optical signal and transmits tens or hundreds of Km, and then converts the optical signal into an electric signal, and the predistortion method uses a main signal. Prediction and measurement of distortion to generate high frequency, but generates a high frequency, but there is a problem that there is no way to control the high frequency above the secondary IMD, and the mixing system of the predistortion method and the feedforward method is complicated by using many electric and optical elements Difficult to control

In addition, the above methods have difficulty in transmitting a wideband wireless signal due to the limited frequency range due to linearization due to the use of many electric elements for linearization.

In addition, the three methods commonly control the distortion signal of the optical transmitter by an electrical system, which causes another distortion signal to be generated for the control of the distortion signal, resulting in a product defect such as a malfunction.

Finally, the existing system was able to control only the specific signal with the most interference on the adjacent channel among the various harmonic and IMD components caused by the nonlinearity of the laser diode. Therefore, there is a problem in that a separate complex system needs to be added to process a plurality of nonlinear distortion signals.

An object of the present invention is to solve the above problems, to provide a non-linear distortion removing device and a method for removing the non-linear distortion generated in the wireless optical transmitter.

Another object of the present invention is to remove nonlinear distortion by removing a third order IMD signal and other nonlinear distortion signals caused by nonlinear components of a laser diode generated by simultaneously modulating and transmitting a plurality of wireless RF signals using mutual gain modulation of ROSA. The present invention provides a non-linear distortion elimination device and a method for eliminating an optical transmitter which can minimize the effect of reducing the performance of the RoF system.

Another object of the present invention is to reduce the non-linear characteristics of the electrical elements as much as possible by using the minimum electrical element for the nonlinear distortion elimination device, in the existing electrical system, coupling the main signal for the distortion signal control, Disclosed are a nonlinear distortion elimination device and an elimination method for an optical transmitter for eliminating another distortion signal that may occur during matching, gain adjustment, and phase shift.

Finally, another object of the present invention, by removing the electrical method in the method of controlling the non-linear distortion generated in the wireless optical transmitter by an optical method, a non-linear distortion removal device for optical transmitters having a relatively simple structure and removal To provide a way.

In order to achieve the above object, the optical transmission distortion elimination apparatus according to the first embodiment of the present invention, the laser diode for generating a second signal by adjusting the amplitude of the first signal; A phase shifter for transforming the phase of the first signal to generate a third signal; And a semiconductor optical amplifier configured to receive a third signal and generate a fourth signal, and receive a second signal and mutually gain-modulate the fourth signal to generate a fifth signal.

In addition, the optical transmission distortion elimination apparatus according to the second embodiment of the present invention, the phase shifter for converting the phase of the first signal to generate a second signal; A laser diode for adjusting the amplitude of the second signal to produce a third signal; And a semiconductor optical amplifier configured to receive a first signal and generate a fourth signal, and receive a third signal and mutually gain-modulate the fourth signal to generate a fifth signal.

In addition, the optical transmission distortion removal method according to an embodiment of the present invention, the first step of the main signal is input and branched; A second step of adjusting magnitude and phase between the branched main signals; A third step of inducing mutual gain modulation in a semiconductor optical amplifier; And a fourth step of transmitting an output signal of the semiconductor optical amplifier.

On the other hand, the non-linear distortion signal removing apparatus according to an embodiment of the present invention, by injecting the output light generated from the laser diode of the wireless optical transmitter into a semiconductor optical amplifier (SOA: Cross-optic amplifier) (XGM: cross gain Modulation) provides a mechanism to remove nonlinear distortion signals. Mutual gain modulation refers to a phenomenon in which when the two optical signals are incident and amplified in an optical gain medium such as a semiconductor optical amplifier, a change in intensity of one light affects the gain of another light. When two optical signals having different and somewhat strong intensities are amplified, when one signal disappears due to gain saturation of the amplifier, the other signal is amplified more than when two signals are simultaneously input. By using this, two distortion signals having the same magnitude and phase can be injected into a semiconductor optical amplifier and removed.

The above and other objects and features and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Fig. 2 is a block diagram showing each structure of a nonlinear distortion signal removing apparatus for an optical transmitter according to a first embodiment of the present invention.

Referring to FIG. 2, the apparatus for canceling a nonlinear distortion signal for an optical transmitter according to an exemplary embodiment of the present invention includes a phase converter 100a, a DFB LD (Distibute Feedback Laser Diode) 200a, and a reflective semiconductor optical amplifier: 300a, or less RSOA).

The phase converter 100a converts the phase of the applied RF signal S1 and supplies it to the RSOA 300a. The phase shifter 100a phase shifts the input RF signal S1 and supplies the RSOA 300a with the nonlinear distortion signal phase of the optical signal generated from the DFB LD 200a to the RSOA 300a. It is the same as the nonlinear distortion signal phase, and it corrects when the circuit phase is out of order and synchronizes it with the specific phase of the circuit.

The DFB LD 200a converts the RF signal S1 into an optical signal and transmits the converted RF signal S1 to the RSOA 300a. At this time, due to the nonlinear characteristics of the DFB LD 200a, a non-linear distortion signal such as a harmonic or IMD3 separate from the main signal is generated in the output signal of the DFB LD 200a. The magnitude of the nonlinear distortion signal among the output signals of the DFB LD 200a should be equal to the magnitude of the nonlinear distortion signal of the optical signal generated in the RSOA 300a according to the output signal of the phase converter 100a. Here, in consideration of the fact that two signals having the same magnitude and phase are removed from the RSOA 300a, it is necessary to vary the magnitudes of the two main signals so that the two main signals do not cause mutual gain modulation. This is the main signal in the process of making the magnitude of the nonlinear distortion signal output from the DFB LD 200a equal to the distortion signal size of another optical signal generated in the RSOA 300a, that is, when adjusting the bias current of the DFB LD 200a. The size of is also adjusted differently from the size of other main signals injected into the RSOA 300a. Therefore, in the RSOA 300a, two nonlinear distortion signals having the same phase and magnitude are removed, and only two main signals having different magnitudes are transmitted to the optical path. That is, the main signal is also scaled in the process of differently supplying the bias current applied to the DFB LD 200a in order to control the magnitude of the nonlinear distortion signal among the output signals of the DFB LD 200a, thereby becoming similar to the size of the nonlinear distortion signal. . Accordingly, two main signals having different sizes are supplied in the RSOA 300a so that mutual gain modulation does not occur.

Meanwhile, in the use of a laser diode, a general laser diode may be used. However, a laser diode according to an embodiment of the present invention may preferably use a DFB laser diode having a high linearity, a wide operating temperature range, and a low noise figure. .

RSOA (300a) is to improve the output of the semiconductor optical amplifier, the AR coating (Anti-Reflection Coating) to the input and output terminals of the semiconductor optical amplifier to make the input and output smooth, HR coating one side of the semiconductor optical amplifier It has a structure made so that light does not leak out by high reflection coating. The RSOA 300a receives the optical signal supplied from the DFB LD 200a and the optical signal supplied from the phase shifter 100a and converted in the RSOA 300a to remove the nonlinear distortion signal using a mutual gain modulation phenomenon. Output only the signal.

The operation principle of the nonlinear distortion elimination apparatus for an optical transmitter according to the first embodiment of the present invention having the above structure is as follows.

3 is a configuration diagram of a non-linear distortion elimination apparatus for optical transmission according to a first embodiment of the present invention, and FIG. 4 is an exemplary view showing an RF frequency spectrum when a signal is transmitted through a RoF link using only DFB LD. 5 is an exemplary diagram showing the RF frequency spectrum of the signal injected into the RSOA through the DFB LD, Figure 6 is an exemplary diagram showing the RF frequency spectrum of the ROSA output signal.

3 to 6, as shown in FIG. 3, in the nonlinear distortion elimination apparatus according to the first exemplary embodiment of the present invention, a signal input from the input terminal 800 is converted into a phase shifter 100a and a DFB LD 200a. The second signal S2 and the fourth signal S4 generated in the RSOA 300a through each other, and the fifth signal S5 from which the nonlinear distortion signal is removed is externally transmitted through the optical link. Send to

As shown in FIG. 4, when the first signal S1 of 1 GHz and 1.1 GHz is supplied to the DFB LD 200a, the DFB LD 200a should not be generated as an output signal of the DFB LD 200a. The component occurs at 900 MHz and 1.2 GHz, with a magnitude of approximately -55 dBm. In order to eliminate this, light to be linearized, that is, a second signal S2 is input into the RSOA 300a to generate a mutual gain modulation phenomenon.

In the non-linear distortion elimination device for optical transmission according to the first embodiment of the present invention, the input terminal 800 supplies the first signal S1 coupled from the first coupler 400a to the second coupler 400b and branches through it. The first signal S1 is supplied to the phase shifter 100a and the DFB LD 200a, respectively. The phase shifter 100a uses the 900 MHz and 1,2 GHz nonlinear distortion signals shown in FIG. 5, that is, the third signal S3 having the phase shifted first signal to be in phase with the IMD3 signal, and the electrical terminal of the RSOA 300a. The fourth signal S4 having the same phase as the IMD3 signal of the output signal S2 passing through the DFB LD 200a is generated in the RSOA 300a.

On the other hand, the first signal S1 supplied to the DFB LD 200a applies the bias current supplied to the DFB LD 200a to a low level, thereby clipping the main signals f ₁ and f ₂ as shown in FIG. 5. As described above, the main signal and the IMD3 component are converted into the second signal S2 having a similar magnitude and supplied to the RSOA 300a through the signal distributor 700. Therefore, as shown in FIG. 6, the RSOA 300a is supplied from the phase shifter 100a and the second signal supplied from the IMD3 signal and the DFB LD 200a among the fourth signals S4 photo-converted in the RSOA 300a. The fifth signal S5 having the reduced IMD3 signal is generated by mutually gain-modulating the IMD3 signal among the signals S2. At this time, an important control variable that causes mutual gain modulation in the RSOA 300a is the magnitude and phase of the IMD3 signal. If the magnitude and phase of the two signals are the same in the RSOA 300a, unnecessary IMD3 components can be removed.

On the other hand, by optimizing the phase and magnitude, an improved spectrum can be obtained at the final stage. As shown in FIGS. 5 and 6, the size of IMD3 at 900 MHz and 1.2 GHz is about -65 dBm, and a carrier-to-noise ratio (CNR) of about 10 dB compared to the case where only the DFB LD 200a is used. It can be seen that the improvement. The fundamental frequency components f ₁ (1 GHz) and f ₂ (1.1 GHz) do not change in size even when the linearization system is applied. The reason is that the magnitude and phase should be almost identical in order to cause the magnitude change due to the mutual gain modulation phenomenon, but the main signal f _{1 ,} f ₂ is clipped by supplying the applied bias current of the DFB LD 200a very low, such as 10 mA. By clipping and applying to the RSOA 300a, the relative magnitude with the main signal applied directly to the RSOA 300a via the phase shifter 100a can be increased to 30 dB or more. Therefore, almost no XGM occurs between fundamental frequencies.

7 is an exemplary diagram illustrating a signal in an RSOA and an output signal according thereto.

Referring to FIG. 7, by adjusting the amount of bias current applied to the DFB LD 200a, the second signal S2 applied to the RSOA 300a, that is, the main signals f _{1 and} f ₂ and the IMD3 signal 2f _1. In addition to adjusting the magnitude of -f _{2 and} 2f ₂ -f ₁ , the phase shifter 100a adjusts the phase of the third signal S3 to eventually adjust the phase of the fourth signal S4. Accordingly, two IMD3 signals having the same magnitude and phase in the RSOA 300a are eliminated by mutual gain modulation.

As described above, in order to eliminate the nonlinear distortion signal by the mutual gain modulation, two signals having the same magnitude and the same phase must be applied to the RSOA 300a.

FIG. 8 is a diagram illustrating a principle of reducing IMD3 due to phase change in RSOA, and illustrates a principle in which two signals having the same phase and magnitude are removed.

Referring to FIG. 8, when the signal of the DFB LD 200a is input in a high state (A), the carrier density change in the RSOA 300a becomes-high state B due to the exhaustion of the carrier. As a result, the output of the RSOA 300a will be at a high state. At the same time, if a high signal of RF signal is applied to the electrical terminal of the RSOA 300a, such as that applied to the DFB LD 200a, the carrier will be placed inside the RSOA. It plays a role of supply (C). Therefore, the output is changed to the state in which the carrier is supplied from the outside in the state in which the carrier is depleted, so that the output is in the state 0 (D). That is, the size of IMD3 to be controlled is zero. Looking closely at this state, it can be seen that the phase of (A) and (C) must be the same in order to bring the final output to zero. As shown in FIG. 5, due to the low bias condition of the DFB LD 200a, the fundamental frequency components 1 GHz and 1.1 GHz are attenuated a lot, which is similar to the magnitude of the IMD3 signal. These frequency components are input into the RSOA 300a and at the same time a frequency component such as IMD3 is input to the electrical terminal of the RSOA 300a. As a result, the mutual gain modulation in the RSOA 300a removes two IMD3 signals having the same phase and magnitude without affecting the fundamental frequency, that is, the main signal.

On the other hand, the first embodiment of the present invention is described in the configuration that the RF signal supplied from the input terminal is applied to the RSOA 300a via the phase shifter 100a, but the RF signal supplied from the input terminal passes through the phase shifter DFB. It may be applied to the LD 200a and supplied to the RSOA 300a. That is, the phase converter 100a may be positioned in front of the DFB LD 200a to phase-shift the RF signal and supply the RF signal to the DFB LD.

9 is a block diagram showing each configuration of a nonlinear distortion elimination apparatus according to a second embodiment of the present invention, Figure 10 is a block diagram of a non-linear distortion removal apparatus for optical transmission according to a second embodiment of the present invention.

9 and 10, in the nonlinear distortion elimination apparatus according to the second embodiment of the present invention, an output terminal of the phase shifter 100b is connected to an input terminal of the DFB LD 200b. Therefore, the first signal S1 is converted into the second signal S2 via the phase converter 100b and applied to the DFB LD 200b.

In addition, another first signal S1 branched through the second coupler 400b is directly applied to the electrical terminal of the RSOA 300b, and thus the RSOA 300b generates the fourth signal S4.

On the other hand, the DFB LD 200b has a second signal whose phase is shifted, adjusts the magnitude to a bias current, generates a third signal S3, and injects the third signal S3 into the RSOA 300b. Therefore, while the phase and magnitude are adjusted to be the same as the IMD3 signal of the fourth signal S4, while the IMD3 signal of the third signal S3 is injected into the RSOA 300b, the two IMD3 signals are removed by the mutual gain modulation phenomenon. The main signals f _{1 and} f ₂ are output and transmitted to the outside via the optical link.

On the other hand, the internal signal processing or operation principle between the components such as the RSOA (300b), DFB LD (200b), and the phase shifter (100b) of the non-linear distortion removal device for an optical transmitter according to the second embodiment of the present invention As described above in the embodiment is omitted.

11 is a flowchart illustrating a method for removing nonlinear distortion for an optical transmitter according to a first embodiment of the present invention.

Referring to FIG. 11, a nonlinear distortion removing method according to an embodiment of the present invention having such a configuration is as follows.

The main signal is input and branched into two signals having the same magnitude and phase (S101).

In step S101, the signal is branched into two main signals having the same magnitude and phase through a coupler and supplied to at least one of the DFB LD, the phase shifter, and the RSOA. Here, the main signal may be supplied to the DFB LD and the phase shifter, respectively, and a signal passed through the phase shifter is applied to the RSOA. In addition, the main signal may be supplied to the RSOA and the phase shifter, respectively. At this time, the signal passing through the phase shifter is applied to the DFB LD. The layout of each component varies depending on how the system is configured, and various variations can occur.

The magnitude and phase between the branched main signals are adjusted (S102).

In step S102, the DFB LD is applied to the RSOA by adjusting the magnitude of the main signal through the bias current amount and adjusting the phase of the main signal through the phase shifter. At this time, the signal applied through the phase shifter is applied to the electrical terminal of the RSOA, thereby generating an optical signal inside the RSOA.

XGM phenomenon is induced in the RSOA (S103).

In step S103, the nonlinear distortion signal is removed by generating an XGM between two optical signals including nonlinear distortion signals having the same magnitude and phase in the RSOA, that is, the optical signals applied through the DFB LD and the other optical signals generated in the RSOA.

Finally, the output signal of the RSOA is transmitted (S104).

In step S104, the output signal of the RSOA from which the nonlinear distortion signal has been removed is transmitted to the outside via the optical link.

On the other hand, in the embodiment according to the present invention, the IMD3 signal of the non-linear distortion signal in the removal of the non-linear distortion signal is representatively described, but is not limited thereto, but also for other non-linear distortion signals such as harmonic distortion components or higher order intermodulation distortion components. Could be applied.

As described above, the non-linear distortion elimination apparatus and the removal method for an optical transmitter according to an embodiment of the present invention, which occurs when a plurality of wireless RF signals are simultaneously modulated and transmitted using a mutual gain modulation phenomenon of the ROSA, a laser diode By removing the 3rd order IMD signal and other nonlinear signals caused by the nonlinear components of, the effect of reducing the performance of the RoF system due to the nonlinearity can be minimized.

In addition, the nonlinear distortion elimination device and the removal method for an optical transmitter according to an embodiment of the present invention, by using a minimum of the electronic device for the nonlinear distortion removal device can reduce the nonlinear characteristics of the electrical device as much as possible, In the system, it is possible to remove another distortion signal which may occur during coupling, matching, gain adjustment, and phase shifting process for the main signal for distortion signal control.

In addition, the non-linear distortion removing device and method for removing the optical transmitter according to an embodiment of the present invention, in the method of controlling the non-linear distortion generated in the wireless optical transmitter, by implementing the optical method away from the electrical method than the conventional system It provides an effect with a simple structure.

Finally, the nonlinear distortion elimination device and method for optical transmitter according to an embodiment of the present invention can be used for wideband signal application, so that it is possible to overcome the modulation frequency range limited by the electric elements mainly used in the existing system. To provide.

In addition, preferred embodiments of the present invention are disclosed for the purpose of illustration, those skilled in the art will be able to make various modifications, changes, additions, etc. within the spirit and scope of the present invention, such modifications and modifications belong to the scope of the claims You will have to look.

Claims (18)

A laser diode for adjusting the amplitude of the first signal to produce a second signal; A phase shifter for converting the phase of the first signal to generate a third signal; And a semiconductor optical amplifier configured to receive the third signal and generate a fourth signal, and receive the second signal and mutually gain-modulate the fourth signal to generate a fifth signal. Nonlinear Distortion Eliminator. The method of claim 1, wherein the laser diode, And generating the second signal whose magnitude is adjusted according to the amount of bias current input. The method of claim 2, wherein the laser diode, And a nonlinear distortion signal included in the second signal equal to the size of a nonlinear distortion signal included in the fourth signal. The method of claim 1, wherein the phase shifter, And adjusting the phase of the non-linear distortion signal included in the fourth signal to be the same as the phase of the non-linear distortion signal included in the second signal. A phase shifter for transforming the phase of the first signal to generate a second signal; A laser diode for generating a third signal by adjusting an amplitude of the second signal; And a semiconductor optical amplifier configured to receive the first signal to generate a fourth signal, and to receive the third signal and to mutually gain-modulate the fourth signal to generate a fifth signal. Nonlinear Distortion Eliminator. The method of claim 5, wherein the laser diode, And generating the third signal whose magnitude is adjusted according to the amount of input bias current. The method of claim 6, wherein the laser diode, And adjusting the size of the nonlinear distortion signal included in the third signal to be equal to the size of the nonlinear distortion signal included in the fourth signal. The method of claim 5, wherein the phase shifter, And a non-linear distortion signal included in the third signal and a non-linear distortion signal included in the fourth signal. The semiconductor optical amplifier according to any one of claims 1 to 8, wherein A non-linear distortion elimination device for an optical transmitter, characterized by a reflective semiconductor optical amplifier. The method according to any one of claims 1 to 8, wherein the laser diode, A non-linear distortion elimination device for an optical transmitter, characterized in that the distributed feedback laser diode. The method according to any one of claims 1 to 8, It further has an input stage, And a coupler for branching the RF signal input from the input terminal into two first signals having the same magnitude and phase and supplying the RF signal to at least one of the phase shifter, the laser diode, and the semiconductor optical amplifier. Nonlinear distortion elimination device for optical transmitter. The method according to any one of claims 1 to 8, A signal splitter is disposed between the semiconductor optical amplifier and the laser diode to distribute the signal. And the signal splitter supplies the signal output from the laser diode to the semiconductor optical amplifier, and supplies the signal output from the semiconductor optical amplifier to the outside through an optical link. A first step in which a main signal is input and branched; A second step of adjusting magnitude and phase between the branched main signals; A third step of inducing mutual gain modulation in a semiconductor optical amplifier; And a fourth step of transmitting an output signal of the semiconductor optical amplifier. The method of claim 13, wherein the first step is A nonlinear distortion elimination method for an optical transmitter, characterized in that a main signal is supplied to at least one of a semiconductor optical amplifier, a laser diode, and a phase shifter. The method of claim 13, wherein the second step, A first substep of adjusting the magnitude of the input main signal according to an amount of bias current applied to the laser diode and converting the input main signal into a first optical signal; A second substep of converting a phase of the main signal by the phase converter and applying the same to the semiconductor optical amplifier; A third substep of generating a second optical signal in the semiconductor optical amplifier according to the signal supplied from the phase converter; And a fourth sub-step of injecting the first optical signal supplied from the laser diode into the semiconductor optical amplifier. The method of claim 13, wherein the second step, A first substep of converting a phase of the main signal by the phase converter and applying the same to the laser diode; A second sub-step of controlling the magnitude of the signal supplied from the phase shifter by the bias current of the laser diode and converting the signal into a first optical signal; A third substep of generating a second optical signal in the semiconductor optical amplifier according to the supplied main signal; And a fourth sub-step of injecting the first optical signal supplied from the laser diode into the semiconductor optical amplifier. The method of claim 15 or 16, wherein the first and second optical signals, It includes a non-linear distortion signal separate from the main signal, the phase and the magnitude between the non-linear distortion signals of the first and second optical signal is the same and the magnitude between the main signal is input into the semiconductor optical amplifier. Nonlinear distortion elimination method for optical transmitter. The method of claim 17, wherein the third step, Non-linear distortion signals having the same magnitude and phase are removed by inducing mutual gain modulation of the two optical signals in the semiconductor optical amplifier, and two main signals having different magnitudes are output without being removed. How to remove the distortion.

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